Unqualified words for professions and animals do not assume either sex in modern usage, but this was not always the case. When Esperanto was created, people or animals not specifically specified female were traditionally assumed to be male. So, instruisto used to be assumed to mean a male teacher, and a female teacher was an instruistino; the title doktoro used to be assumed to be a man with a doctorate, for a woman it was doktorino. With animals, a bovo was assumed to be a bull, a cow was a bovino. Nowadays, instruisto means a teacher of either gender, though bovo may be either a head of cattle or a bull.

In modern usage, one should only assume a particular sex for family relationships, such as patro ‎(“father”)/patrino ‎(“mother”), edzo ‎(“husband”)/edzino ‎(“wife”), frato ‎(“brother”)/fratino ‎(“sister”), and certain titles, such as sinjoro ‎(“Mister”)/sinjorino ‎(“Missus”), fraŭlino ‎(“Miss”), damo ‎(“Dame”).

A common idiom to designate male animals is to make compounds with viro ‎(“man”), such as virbovo for bull (although unidiomatically, this could mean a minotaur). L.L. Zamenhof, the founder of Esperanto, began this usage in the 1920s with his translation of Genesis, and it is now widespread. To designate male professionals, it is common to use the adjective vira, such as virakelnero for a male waiter.

Of the several neologisms coined to be a male counterpart to -in-, the most frequently used is -iĉ-, which has appeared in some books, but does not have official recognition. For example, boviĉo would be a bull like bovino is a cow, and in such usage bovo would only be a head of cattle.